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One DNA nucleotide change results in one amino acid change. This is called "missense mutation"

Question

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One DNA nucleotide change results in one amino acid change. This is called "missense mutation"

BlackTom AI · Accepted Answer

A missense mutation is a single-base substitution in the coding sequence that changes a codon so it specifies a different amino acid. This is the key definition: one nucleotide change → codon altered → different amino acid incorporated.

Relevant concepts:
- The genetic code is read in triplet codons (mRNA) that specify amino acids.
- A point mutation (single-nucleotide substitution) in a codon can have three outcomes: silent (synonymous), missense (different amino acid), or nonsense (stop codon).
- Missense mutations can be conservative (similar amino acid) or nonconservative (very different), affecting protein function to varying degrees.

Step-by-step reasoning with an example:
1. Take the mRNA codon GAA, which encodes glutamic acid (Glu).
2. A single-nucleotide substitution at the second position (GAA → GUA) changes the codon to one that encodes valine (Val).
3. That single-base change therefore results in one amino acid being replaced by another in the polypeptide chain — a classic missense mutation.

Why this is correct:
- The definition of “missense mutation” precisely matches “one DNA (or RNA) nucleotide change results in one amino acid change.” Thus the statement is true when a single-nucleotide substitution alters the codon meaning.

Why the alternative (i.e., false) would be incorrect:
- Not every single-nucleotide change produces an amino acid change (silent mutation due to codon redundancy), and some single-nucleotide changes produce a stop codon (nonsense mutation). Insertions/deletions (frameshifts) typically change many downstream amino acids. But the statement describes the specific scenario that does produce one amino acid change — which is the missense case.

Conclusion: The statement is True; a single nucleotide substitution that changes a codon to one encoding a different amino acid is called a missense mutation. This matches the provided answer: True.

T/F One DNA nucleotide change results in one amino acid change. This is called "missense mutation"判断题

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